Some inferences on the mechanism of atmospheric gas/particle partitioning of polycyclic aromatic hydrocarbons (PAH) at Zaragoza (Spain)

Gas-particle partitioning of pollutants is an important mechanism determining atmospheric processing and its impact to environmental and human health. In this paper, the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAH) has been studied with the aim of determining the main mechanism of PAH partitioning in Zaragoza (Spain) aerosols. To reach this goal, the ambient concentrations of PAH (gas and particle phase) collected in this city for one year period (2003-2004) have been analyzed. The partitioning between the particle and gas phases was studied according to three different models: the Junge adsorption model, the absorption into the organic matter model using the octanol-air (KOA) partition coefficient and the absorption into the organic matter plus the adsorption onto the soot carbon model using the soot-air (KSA) partition coefficients. Experimental gas/particle partition coefficients (KP) correlated well with the subcooled liquid vapour pressures (P0 L) of PAH but with slopes higher than the expected value of - 1. Experimental Kp values were well fit to the modelled ones when, in addition to absorption into organic matter, adsorption onto the soot carbon was considered. It could be concluded that the main partition mechanism in Zaragoza aerosols was explained by adsorption onto the soot carbon. However, Kp modelled values were affected by the different thermodynamic parameters related to soot types. The influence of the organic matter and elemental carbon fractions on the Kp modelling was also studied. The different particle characteristics, local factors, the presence of non exchangeable fraction and non equilibrium were considered like main keys to explain deviations of the experimental Kp values from predictions according to models.Authors would like to thank the Government of Aragón (DGA) for the grant to M.T.C and the Spanish Government for the JAE doctoral contract to J.M.L and for the Juan de la Cierva contract to M.V.N.Peer reviewe

Study of Pb sources by Pb isotope ratios in the airborne PM10 of Zaragoza, Spain

Lead is a toxic trace element which produces harmful effects on human health, even at low concentrations, and it can be useful as ambient pollution tracer because the relative abundance of its four stable isotopes (204, 206, 207 and 208) depends on the emission source. This study was focused on the lead concentrations and isotope ratios in the PM10 of Zaragoza, in order to determine the main Pb pollution sources and to check whether the influence of the prohibition of leaded fuel was worthwhile. Two sampling campaigns from 2001 until 2004, the first one in which leaded gasoline was still effective and the second one with the phase-out, were carried out by using a high-volume air sampler able to trap the particulate matter equal to or less than 10 µm (PM10) on Teflon-coated fibre glass filters. Firstly, the Pb concentrations for the two sampling campaigns were analysed by inductively-coupled plasma optical emission spectrometry (ICP-OES). No statistically significant decrease in the Pb average concentration was obtained from the first to the second sampling. Enrichment factors showed that anthropogenic sources were prevalent during both samplings, in particular during 2001–2002. Afterwards, only those samples with higher concentrations than the limit of quantification of Pb were analysed to determine the lead isotopic composition by inductively-coupled plasma quadrupole mass spectrometry (ICP-QMS). To apply this analytical technique successfully, it was necessary to optimize the parameters affecting the measurement accuracy and precision. Differences were found regarding the lead isotope ratios for both periods finding that anthropogenic sources related to industrial processes were reflected on both campaigns. The gasoline contribution for the first campaign was 23% whereas for the second sampling this contribution was negligible, corroborating the success of the lead policies on the quality of the environment.Peer reviewe

Comparison of receptor models for source apportionment of the PM10 in Zaragoza (Spain)

Receptor models are useful to understand the chemical and physical characteristics of air pollutants by identifying their sources and by estimating contributions of each source to receptor concentrations. In this work, three receptor models based on principal component analysis with absolute principal component scores (PCA-APCS), Unmix and Positive Matrix Factorization (PMF) were applied to study for the first time the apportionment of the airborne particulate matter less or equal than 10 m (PM10) in Zaragoza, Spain, during one year sampling campaign (2003-2004). The PM10 samples were characterized regarding their concentrations in inorganic components: trace elements and ions and also organic components: polycyclic aromatic hydrocarbons (PAH) not only in the solid phase but also in the gas phase. A comparison of the three receptor models was carried out in order to do a more robust characterization of the PM10. The three models predicted that the major sources of PM10 in Zaragoza were related to natural sources (60%, 75% and 47% respectively for PCA-APCS, Unmix and PMF) although anthropogenic sources also contributed to PM10 (28%, 25% and 39%). With regard to the anthropogenic sources, while PCA and PMF allowed high discrimination in the sources identification associated with different combustion sources such as traffic and industry, fossil fuel, biomass and fuel oil combustion, heavy traffic and evaporative emissions, the Unmix model only allowed the identification of industry and traffic emissions, evaporative emissions and heavy duty vehicles. The three models provided good correlations between the experimental and modelled PM10 concentrations with major precision and the closest agreement between the PMF and PCA models.Peer reviewe